1. Field of the Disclosure
The present invention relates to an electrophoretic display device, and more particularly, to an electrophoretic display device which includes electrophoretic dispersion liquid internalized on a lower substrate, and a method for manufacturing the same.
2. Discussion of the Related Art
In general, an electrophoretic display device refers to a device capable of displaying images using electrophoresis wherein colored charge particles are moved by an electric field applied from the outside. Here, ‘electrophoresis’ means a phenomenon that charged particles are moved in electrophoretic dispersion liquid (electrophoretic ink) by coulomb forces when an electric field is applied to the electrophoretic dispersion liquid having the charged particles dispersed therein.
An electrophoretic display device using electrophoresis has a bistability that allows original images to be displayed for a relatively long time even if an applied voltage is removed. In other words, the electrophoretic display device can maintain a specific screen for a relatively long time without voltages being continuously applied thereto. As a result, the electrophoretic display device may be applied to e-books which do not require quick changes of screens.
Moreover, an electrophoretic display device has no dependence on viewing angle and can provide images that are comfortable to eyes remarkably enough to be similar to paper, unlike a liquid crystal display device. As a result, demands for the electrophoretic display devices have been increasing.
FIG. 1 is a sectional view illustrating a structure of a display device according to the related art.
With reference to FIG. 1, an electrophoretic display device includes lower and upper substrates 10 and 20 bonded to each other with an electrophoretic film 30 disposed between the lower substrate 10 and the upper substrate 20. The electrophoretic film 30 includes first and second adhesive layers 34 and 36 formed of a transparent material, a common electrode 38 formed of a transparent conductive material, and a plurality of microcapsules 32 having electrophoretic dispersion liquid therein.
Although not shown in FIG. 1, a plurality of pixel electrodes (not shown) are formed on the lower substrate 10 opposite to the common electrode 38 that is formed on the upper substrate. A plurality of thin film transistors (TFT, not shown) are also formed on the lower substrate 10 to apply voltages to the plurality of the pixel electrodes as switching devices. Microcapsules 32 are provided with electrophoretic dispersion liquid (electrophoretic ink). The electrophoretic ink includes positive (+) charged particles and negative (−) charged particles provided therein. The charged particles provided in the microcapsule 32 are moved by electrophoresis, thereby presenting an image.
In the related art electrophoretic display device, the upper substrate 20, the lower substrate 10 and the lamination type electrophoretic film 30 are manufactured separately. After that, the electrophoretic film 30 is disposed between the lower substrate 10 and the upper substrate 20.
The electrophoretic film 30 is attached to the upper substrate 20 and a release film is kept attached to a first adhesive layer 34. Just before it is laminated on the lower substrate 10, the release film is eliminated. After that, the electrophoretic film 30 is attached to the lower substrate 10 by the first adhesive layer 34.
As a result, the lower substrate 10, the upper substrate 20 and the electrophoretic film 30 have to be manufactured separately and the manufacturing process of the related art electrophoretic display device is disadvantageously complicated. Thus, the manufacturing of the electrophoretic display device requires a lot of time and productivity deteriorates. The electrophoretic film 30 additionally has to be manufactured and production cost is increased.
To overcome the disadvantages of the related art electrophoretic display device, technology that enables the electrophoretic layer to be internalized in the lower substrate has been proposed. However, a structure and a manufacturing process technology for internalizing the electrophoretic layer on the lower substrate have not been developed to levels to address such problems. As a result, it is difficult to apply the technology to actual production.
The related art electrophoretic display device has a further disadvantage of lost charging properties of the charged particles filled into cells provided in the lower substrate. As a result, stability and driving reliability of the charged particles is reduced. In addition, contrast of pixels is deteriorated and a display quality might be deteriorated accordingly.